Method of and apparatus for producing tapped resistors



W. LEATHERS METHOD OF AND APPARATUS FOR PRODUCING TAPPED RESISTORS May Filed April 18,

e r s g-aadcsl ATTORNEY.

lNVENTOR. AAA/Q dew-"Fae? a Patented May 18, 1943 METHOD OF AND APPARATUS FOR PRO- DUCING TAPPED RESISTORS Ward Leathers and Jerrier Haddad, Brooklyn,

N. Y., assignors to International Business Machines Corporation, New York, N. Y., a corporation of New York Application April 18, 1942, Serial No. 439,541

Claims.

The present invention relates to a method of and apparatus for automatically producing precision-tapped wire-wound resistors, particularly resistors which are tapped at points which are unequally spaced from one another and which consequently represent resistance values alongthe length of the resistor which are of progressively increasing values but which may vary in their arithmetical progression according to predetermined prerequisites.

Heretofore various machines have been designed for producing such tapped resistors automatically and in the main these machines have been dependent for their operation either on the number of turns effected upon the resistor core or form to produce the various tap points or upon the spacing of the various taps one from another. Where consideration has been given to the number of turns of wire upon the resistor core, it has been necessary to take into account the diameter of the core form, the diameter or gauge of the wire employed, the material of which it is formed, and the character or closeness of the spacing effected between adjacent turns as well as other considerations, such as the tension applied to the wire during winding, the temperature conditions during the winding operation, etc. Even with all of these considerations carefully accounted for in the design and operation of such machines, consistent and accurate precision work has not been attained due to uncontrollable considerations such as discrepancies in uniformity of the core dameter or of the wire diameter. Where precision spacing of the tap points has been resorted to the results have been even less determinate with the result that such methods have been reserved mainly for the production of non-precision resistors where wide tolerances'are permitted, leaving the production of precision resistors to hand operations or to semi-automatic processes wherein the winding operation is stopped during accurate determination of the various tapped points.

The present invention is designed to overcome many of the various limitations that are attendant upon the automatic production of precision resistors of the character set forth above and has for its principal object the provision of an apparatus which will automatically apply the wire to the resistor core by a progressive winding operation and which will automatically terminate the winding operation at such time as the resistance of the wound wire actually reaches a predetermined definite magnitude.

the invention contemplates the provision of a method and apparatus whereby the resistance value of the wire may be measured during its application to the resistor core and the winding operation terminated when a predetermined resistance value has been reached so that a tap may be made and the winding operation continued until another predetermined resistance value is reached with the process being repeated until such time as the desired number of taps have been completed.

The invention further contemplates the use of electronic means utilizing vacuum tubes whereby the various predetermined desired values of resistance may be sharply discriminated and whereby a series of marginal relays may be actuated in succession to terminate the winding operations and permit the tapping operations to be performed on the partially wound resistor at precisely the proper points for precision accuracy in the final product.

With these and other objects and advantages in view, which will become readily apparent as the nature of the invention is better understood, the invention consists in the novel construction, combination and arrangement of parts shown in the accompanying drawing, in which the figure is a schematic view of one form of an apparatus constructed in accordance with the principles of the present invention.

Referring now to the drawing in detail, the resistance winding machine is designated in its entirety at l0 and is for the most part conven tional in its design insofar as its mechanical features are concerned. In the accompanying drawing the machine [0 has been illustrated purely in diagrammatic form and no claim is made herein to any novelty associated with the mechanical arrangementof parts thereof except possibly insofar as they are conducive toward certain electrical function that will become apparent presently.

The apparatus I 0 involves in its general organization a rotary spindle l2 upon which the resistor forms II are adapted to be received and rotated during the winding operation. The spindle is driven from an electric motor M through a gear train generally characterized by the numeral l6. Conventional shaft couplings [8 permit the spindle to be removed from its operative winding position to facilitate removal of wound forms M from the spindle and the substitution of unwound forms in their place.

The spindle assembly is coupled through a In carrying out the above mentioned object, chain and sprocket assembly 20 to a feed screw 22 which serves upon rotation thereof to move a spool carriage 24 at a relatively slow rate in a direction parallel to the longitudinal axis of the spindle I2 for scanning purposes during the actual winding operation. The carriage 24 is thus moved in timed relation to the speed of rotation of the spindle I2 in order that the resistance wire may be evenly wound on the latter.

The resistance wire 26 is fed from a freely rotat'able spool 28 mounted on the carriage in any suitable manner through a guide 38 from whence it passes underneath a contact-making tensioning spring element 32 before passing to the form I4.. One end of the resistance wire 26 is electrically connected at 34 to a conductive ring 36 which may form a permanent part of the wound resistor and an electrical brush 38 makes slidin contact with the conductive ring 36 so that the total value of ohmic resistance of the wound portion of the wire 26 at any particularinstant may be measured across the brush 38 and contact-making spring element 32.

The motor M is adapted to be driven from a battery B or other suitable source of power. The motor circuit which includes the battery B also includes a normally closed pair of contacts 48 controlled by a relay R which, upon energization of the latter, become opened to break the motor circuit and stop the motor automatically. A starting switch 42 is also contained in the motor circuit and is employed for starting the motor or -sfor stopping the same manually.

According to the present invention means provided for establishing current flow in a signalling or relay-actuating circuit during actual winding of the resistance wire 26 on the form I4 and including the portion of the resistance wire which is actually wound thereon at any particular instant. Means in the form of an electroniccontrolled system of marginally biased relays for obtaining sharp discrimination between the constantly increasing voltage increments in the circuit at the proper intervals and the system is so adjusted that when a predetermined value of resistance wire has been wound on the resistance form, a work circuit is closed through a stepping switch which is automatically maintained in phase with the progressive series of taps being effected at the winding machine with the net result that the relay actuated pair of contacts 40 contained in the motor circuit automatically be comes opened and the motor is stopped for tapping purposes at the resistor in the winding machine.

Accordingly, the signalling circuit in which the brush 38 and contact-making element 32 are contained includes a battery B and a resistor 44 which, because of its series relation to that portion of the resistance wire 26 which is applied to the form l4 at any particular instant, will divide the varying voltage existing in the circuit with that portion. The brush 38 is connected to the positive terminal of the battery B and the contact-making spring 32 is connected to one side of the resistor 44. The other side of the resistor is connected to the negative terminal of the battery B. Thus in the signalling or relay-actuating circuit the voltage existing across the two contact-making elements 38 and 32 is a function of the wound resistance wire 26 and the value of the resistor 44. In this circuit the voltage existing across the two contact-making elements 38 and .32 has a value represented by the formula RggE Rad- 44 where Ra represents theresistance oi the wound.

portion of the wire 26; R44 represents the resistance oi the resistor 44 and E represents the po- .tential delivered by the battery B. The voltage across the two contact-making elements therefore is of an increasing nature but is not proportional to the resistance of the wound portion of the wire 26.

Resistors of the character set forth above which are provided with taps atvarying points along th length thereof are found useful in certain telemetering systems wherein information is relayed to a central station in terms of Arabic numerals. Thus for illustrative purposes the apparatus disclosed herein is designed to produce tapped resistors having ten taps thereon at varying points. Under these circumstances it will be seen that in the relay-actuating circuit provision.

must be made for interrupting the winding operation ten times for the purpose of application to the wire 26 of ten taps.

Accordingly, the brush 38, which is positive with respect to the brush or spring 32, is connected to the grids of ten vacuum tubes, El, E2, E3, E4, E5, E6, E1, E8. E9 and Elli. The cathodes of these tubes are connected to the contactmaking spring 32 through suitable biasing devices which are preferably in the form of batteries. The tube El is given arbitrarily a bias of a: volts by means of a biasing device 39 which may be either a battery or a resistor, dependingnpon the characteristic of the tube. so that a predetermined voltage, when impressed across the brushes 38 and 32, will counteract this bias voltage. When the signal voltage (the voltage across the-brushes 38 and 32) is sufliciently developed to overcome the tube bias it will permit suiiicient plate current to flow to cause a relay RI in the plate circuit oi? the tube to become fully energized.

The tube E2 may arbitrarily be given a bias of a:+3 volts by means of a similar biasing device 33, and thus a signal of three volts more than is required for the tube EI will be required for the tube E2 to permit suflicient plate current to flow therethrough to fully energize a corresponding relay R2 in its plate circuit. The relays R3, R4, R5, R6, R1, R8, R9 and RIO in the plate circuits of their respective tubes E3, E4, E5, E6, E1, E8, E9 and EIO operate in a similar manner and all of the relays are designed to operate on the same amount of current flow therethrough. Each successive tube in the series may be biased by means of respective biasing devices 39 to the extent of three volts more than the preceding tube in the series to give the desired marginal biasing effect to the system.

The relays RI to RIIl, inclusive, are potentially connected in series-and each controls the closing of a work circuit, of which there are ten, leading to respective contacts CI, C2, C3, C4, C5, C6, C1, C8, C9 and Cl 8 of a stepping switch 48 and having a common circuit wire designated at 50 leading to the negative side of a battery B2 and also to the relay R. Each relay in addition to closing a respective work circuit also operates to open all of the work circuits controlled by the previous relays in the series. It is evident that when enough signal voltage is developed in the sigmentioned relay will therefore in eifect become the only operative relay in the series.

The stepping switch It includes a sweep-arm or brush I2 which is connected to a solenoid B. This latter solenoid is adapted to operate a ratchet mechanism generally characterized at II and at the same time close a pair of contacts II which, upon closing. serve to energize the relay R which in turn opens the contacts II to stop the motor and closes a pair or holding contacts II for maintaining the relay R in its energizing circuit. Once closed, the contacts it will maintain the relay R energized and the motor circuit closed until the relay circuit is broken manually by means of a circuit opening device II.

In the operation of the apparatus when it is desired to wind a resistance unit, one end oi the wire 26 is passed over the guideway 3| and beneath the tensioning spring 32 and is secured to the conductive ring 36. Thereafter, upon closing oi the switch 42, the motor M will set the winding apparatus l into operation. As the ohmic value of the resistance wire 28, which is wound upon the form l4 builds up, an increasingly larger signal voltage will occur in the signalling circuit between the brushes 3! and 32. When a predetermined amount of ohmic resistance has been built up in the circuit, this voltage will be suillcient to overcome the bias applied to the first relay RI of the series. Upon energization of this relay a work circuit is completed leading to the contact CI of the steppingswitch 48 and the coil RI is energized by means of the battery B2. The coil R operates to step the switch 48 so that the arm 52 moves to the contact C2 while at the same time the contacts 58 are closed. The relay R is thereby energized and, upon such energization, is locked by virtue of the closing of the contacts 58. Because of the fact that the contacts 40 become opened upon energization of the relay R, the motor circuit is opened and the motor M stops.

At this point in the sequence of operations, a tiepoint or lug may be soldered or otherwise electrically connected to the wire 28. If desired, the wire may simply be looped in the manner indicated at 52. Thereafter the circuit opening device 80 may be depressed to open the circuit through the relay R and permit the motor circuit to be again closed so that resumption of the operation of the winding machine II will take place. The resistance wire 26 will continue to be wound on the form ll until such time as the signal voltage built up in the signalling circuit is sufllciently great to cause operation of the second relay R2 in the series. When this occurs, the motor M is again stalled in the manner previously described and a second tiepoint or lug may be attached to the wire 26.

Each successive tap is made in the same manner until such time as the entire resistor containing ten taps, as specified above, is wound. The completed and tapped resistor may be then removed from the spindle i2 and a new form may be substituted in its place.

The invention is susceptible to considerable modification and it will be understood that other forms of resistance winding machines than that shown in the accompanying drawing may be resorted to if desired. Furthermore, other marginal relay systems than that illustrated may be employed if desired. Such electronic relay systems may be either electrically biased or mechanically biased or various well known pyramidal types of relays employing one or more amplifier systems herein described. The particular biasing set forth in this specification wherein each or the tubes El to Ell, inclusive, differs from the next preceding tube bias in the series by three volts is by no means critical and various biasing combinations may be employed to vary the placement of the taps on the resistor. Similarly, by utilizing a greater or lesser number of relays and a corresponding greater or lesser number of contacts at the stepping switch I, a greater or lesser number of taps will be accommodated at the winding machine.

While the method employed herein has been described in connection with wire-wound tapped resistors, it is obvious that by suitable modification the same may be applied to other types of resistors, such as, for example, untapped wirewound resistors or metalized resistors, whether tapped or untapped, and wherein the metalized operation is carried out by a spring or other process.

The various hand operations such as the application to the wire 28 of the taps 62, the closing of the switch 42, and the restarting of the motor by means of the circuit closing device 80 may be completely dispensed with and the machine converted from a semi-automatic type of machine to a fully automatic type. The invention is therefore to be limited only to the extent that it has been pointed out in the accompanying claims.

What is claimed is:

1. The method of producing a tapped precision resistor of the wire-wound type which comprises winding a resistance wire upon a resistor form continuously while simultaneously connecting the applied portion of the wire in a signalling circuit to produce a continuously changing voltage difierential therein, marginally biasing a series of relay circuits, utilizing the voltage differential thus produced in the signalling circuit to overcome the bias placed upon one of said marginally biased relay circuits, causing said marginal relay circuit to terminate the winding'operations, tapping the wound resistance wire at its point of maximum resistance, resuming the winding operation with the overall applied portion of the resistance wire in the signalling circuit, and repeating the process with the use of additional marginally biased relay circuits until completion of the resistor.

2. The method of producing a precision tapped resistor of the wire-wound type which comprises winding a resistance wire upon a resistance form continuously while simultaneously connecting the applied portion of the wire in a signalling circuit including a current source and a fixed resistor in series therewith, marginally biasing a series of relay circuits, causing the resultant constantly increasing voltage developed in said circuit across the wound portion of the wire to overcome the bias placed upon one of said marginal relay circuits, utilizing said marginal relay circuit to terminate the winding operations,

tapping the wound resistance wire at its point of maximum resistance, resuming the winding operation with the overall applied portion of the resistance wire in the signalling circuit, and repeating the process with the use of additional marginally biased relay circuits until completion of the resistor.

3. The method of producing a tapped precision resistor which comprises applying resistance material to a resistance form continuously while simultaneously connecting the applied -portion thereof in a resistance circuit to produce a continuously changing voltage diflerential therein,

marginally biasing a series of relay circuits, utilizing the voltage diflerential produced in the resistance circuit to overcome the bias placed upon one of said marginal relay circuits, utilizing said marginal relay circuit to terminate the applying operations, tapping the applied resistance material at its point of maximum resistance, resuming the applying operation with the overall applied portion of the resistance material in the signalling circuit, and repeating the process with the use of additional marginally biased relay circuits until completion of the resistor.

4.- The combination with a resistance winding machine including a rotary winding form and means for continuously winding a resistance wire thereonto to produce a series of resistance windings, of a signalling circuit including a resistor and a current source, means for continuously connecting the wound portion of the resistance wire 1!. said circuit in series with said resistor and current source to produce a continuously increasing voltage difierential in the circuit, a plurality of marginally biased electronic-controlled marginal relays connected in parallel to said circuit, an output circuit for each relay, said relays being operable successively upon increases in voltage in the signalling circuit to close their respective output'circuits, and means operable upon closing of each of said output circuits for rendering said winding means inoperative.

5. In an apparatus for producing precision wire-wound resistors, a rotary winding form,

means for feeding a resistance wire thereto to produce a series of resistance windings thereon, a motor for driving said winding form, a motor circuit therefor, a signalling circuit including a resistor and a current source, means-for connecting a wound portion of the resistance, wire in the circuit in series with the current source and resistor continuously during the winding ope'ra- 

